Apparatus in the production of a package or a packaging material

ABSTRACT

An apparatus in the production of a package or a packaging material comprising at least one metal layer and one polymer layer, the apparatus including an inductor connectable to a high frequency current source. According to the invention, said inductor includes a core ( 1 ) of a ferromagnetically conductive material, the core displaying two shanks ( 5   a   , 5   b ) with an air gap ( 6 ) between a first respective end of these shanks ( 5   a   , 5   b ), as well as an arc section ( 7 ) which interconnects a second respective end of the two shanks ( 5   a   , 5   b ) with each other for conducting a magnetic flow ( 8 ) between the shanks, the arc section ( 7 ) displaying an electrically conductive coil ( 2 ) wound around same, the coil displaying connection points ( 3   a   , 3   b   , 11   a   , 11   b   , 11   c ) for said high frequency current source ( 4 ).

TECHNICAL FIELD

[0001] The present invention relates to an apparatus for utilisation inthe production of a package or a packaging material comprising at leastone metal layer and one polymer layer, the apparatus including aninductor connectable to a high frequency current source.

BACKGROUND ART AND PROBLEMS

[0002] It has long been known within the packaging industry to employpackaging materials including outer layers of thermoplastic, which outerlayers may be sealed to one another by fusion after heating andcompression, for obtaining tight and durable sealing joints. Thepackaging material may thus, after forming, e.g. by folding or othermeans, be caused to retain its given configuration in that the outerlayers of the packaging material are brought into abutment against oneanother and sealed to one another. One form of package production whichhas come into considerable use resides in the concept that a web of apackaging material (packaging laminate), comprising a core layer ofpaper or paperboard, a metal layer (normally aluminium) and layers ofthermoplastic disposed outermost, is formed into a tube by thelongitudinal edges of the web being brought together to one another inan overlap joint, whereafter the web edges are sealed to one another.The thus formed tube may then be filled with the contemplated contents,e.g. a liquid, whereafter the tube filled with liquid may be dividedinto individual containers by transverse sealing of the tube alongnarrow zones which are applied at uniform spacing from each other. Thesealed tube sections can, prior to or in connection with the transversesealing, be given a permanent configuration, e.g. a parallelepipedicconfiguration, by folding of the material, whereafter the closed tubesections can be separated from the remainder of the tube and form anindividual, finished consumer package.

[0003] It is known to facilitate the sealing of the packaging materialby utilising an inductor which consists of an electric conductor towhich the desired form has been imparted and which forms one or morecoil turns and which is connected to a current source which supplies thecoil with high frequency alternating current. When this high frequencyalternating current is led through the coil or inductor, a highfrequency magnetic field occurs around it, and when the coil is placedadjacent a material containing a metal layer, induction currents areinduced in this metal layer, which give rise to thermal energy in thoseparts of the metal layer which lie proximal the coil. By the generatedheat, a layer of thermoplastic material, e.g. polyethylene, lyingadjacent the metal layer will soften or melt. When two such layers ofthermoplastic material are compressed against each other, thethermoplastic layers, in the region of the heating, will fuse togetherfor the formation of a tight and durable joint. The width of the jointwill, in this instance, be as wide as the coil wire/inductor conductorwhich abuts against the packaging material.

[0004] Prior art apparatuses for induction sealing of strips andlongitudinal joints certainly function well, but in, for example, thedevelopment of high speed output machines, there is room for improvementin particular because of problems relating to the compression and thetime which is required for the sealing operation. There is also a needin the art for a sealing apparatus which may be utilised for the spotheating of a clearly defined area, preferably on a moving material web.Also in connection with the development of opening arrangements forpackages, there is a need for a sealing apparatus which may be utilisedfor spot heating.

[0005] Another problem in connection with the production of packages orpackaging laminates is to be able to remove loose material, so-calledconfetti, when an emptying hole is prefabricated through which thepackage is intended to be emptied of its contents. In such instance, aprefabricated emptying hole is made only partly, by means of incisionlines through the packaging laminate, from the one side of the laminate,i.e. through a paper or paperboard web coated with a liquid-tightcoating, but not through a subjacent metal foil. The problem in suchinstance is to be able, in a thoroughly controlled manner, to remove theformed parts of the coated paper or paperboard, i.e. the confetti,located inside the incision lines and which are still laminated to themetal foil. The technique for making prefabricated emptying holes isdescribed in the applicant's copending patent application SE-AO-9903315,whose contents are hereby incorporated by reference.

OUTLINE OF THE INVENTION

[0006] The object of the present invention is to disclose an improvedapparatus for utilisation in the production of a package or a packagingmaterial comprising at least one metal layer and a polymer layer, theapparatus including an inductor connectable to a high frequency currentsource. In particular, the present invention has for its object toovercome or obviate the above-mentioned problems and thereby disclose animproved apparatus for induction sealing of, for example, longitudinaljoints, strips, opening arrangements etc., which can be utilised forcontinuous sealing, but which also makes for spot heating. In addition,the present invention has for its object particularly to disclose anapparatus for induction heating of a prefabricated emptying hole in apackaging material, so that a confetti of paper or paperboard may beblistered free from a metal layer, normally an aluminium foil layer,against which it is laminated. In such instance, it is also an object ofthe present invention to gain ready access to this confetti with a tool,e.g. a vacuum tool, for removing it, at the same time as the inductionapparatus is placed at the prefabricated emptying hole.

[0007] These and other objects will be attained by means of an apparatusaccording to the present invention, as this is disclosed in appendedclaim 1.

[0008] In particular, the apparatus according to the present inventionis based on the inventive concept that the coil proper of the inductorneed not necessarily abut against or even be disposed to lie close tothe packaging material in which it is induce current. Instead, aferromagnetic concentrator is advantageously utilised according to thepresent invention which leads the electromagnetic field to a positionproximal the packaging material or in abutment thereto. According to onepreferred embodiment of the invention, this ferromagneticconcentrator/core is moreover designed so that it concentrates theelectromagnetic field in an air gap between two shanks, which impliesthat a considerable electromagnetic field may occur in a position wherethe inductor does not directly abut against the packaging material. Thisis of particular advantage when it is necessary to gain access to thepackaging material with a device, e.g. a (vacuum) tool or the like forremoving, for instance, a confetti. Thanks to the air gap with theelectromagnetic field, the interesting part of the packaging material isaccessible from both sides.

[0009] The apparatus according to the present invention moreoverdisplays at least the advantages that there will be obtained a highlyuniform thermal image in the metal layer of the packaging material, thatit is possible to achieve an extremely high degree of efficiency byadapting the winding of the coil, in particular the number of turnswhich this is wound, and by a capacitor for setting resonance frequency,and that no extra transformer for the apparatus is normally required.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

[0010] The present invention will now be described in greater detailhereinbelow, with reference to a number of preferred embodiments and tothe accompanying Drawings, in which:

[0011]FIG. 1 shows one embodiment of an apparatus according to thepresent invention, seen from the side in perspective;

[0012]FIG. 2 shows the apparatus according to FIG. 1 seen from the sideand abutting against a packaging material;

[0013]FIG. 3 shows induced current circles in the metal layer of apackaging laminate with an inductor according to the present inventiondisposed thereunder, seen from above:

[0014]FIG. 4 shows one preferred apparatus according to the presentinvention seen from the side and abutting against a packaging material;

[0015]FIG. 5 shows an alternative method of winding the coil in anapparatus corresponding to that illustrated in FIG. 1, seen in crosssection through the core and the coil; and

[0016]FIG. 6 shows the coil according to FIG. 5 seen from the side incross section, without core.

DETAILED DESCRIPTION OF THE DRAWINGS AND EMBODIMENTS

[0017]FIGS. 1 and 2 show an apparatus according to the present inventioncomprising a concentrator/core 1 of a ferromagnetically conductivematerial, which preferably displays a permeability of μr 500-8,000, andeven more preferably μr 2,000-8,000, as well as a core 2 of anelectrically conductive material, e.g. copper or silver, which displaysconnection points 3 a, 3 b, 11 a, 11 b, 11 c for a high frequencycurrent source/generator 4.

[0018] The embodiment of the core 1 shown in FIGS. 1 and 2 is designedas a U with two shanks 5 a, 5 b which point in towards the centre lineand are disposed at the ends of the U. Between a first end of a firstshank 5 a pointing in towards the centre line and a first end of asecond, mirror-reversed shank 5 b pointing in towards the centre line,there is an air gap 6. This air gap 6 normally is of a length x of atleast 5 mm, preferably at least 10 mm, but less than 50 mm, preferablyless than 40 mm and even more preferably less than 30 mm, seen in adirection of extent of said air gap 6 between the first respective endsof said shanks 5 a and 5 b. Said shanks moreover normally display awidth y of least 10 mm, but, according to a first preferred embodiment,less than 50 mm, preferably less than 40 mm and even more preferablyless than 30 mm, seen in a direction of extent of extent at right anglesto the direction of extent of said air gap 6, between the firstrespective ends of said shanks 5 a and 5 b, i.e. corresponding to thewidth of the core 1. However, according to a second embodiment, thewidth y may be as much as up to 200 mm, but preferably at most 150 mm.This second embodiment may, for example, conceivably be used inconnection with the sealing of longitudinal joints etc.

[0019] The second ends of the shanks 5 a, 5 b, i.e. those which faceoutwards from the centre line, are connected by an arc section 7 of thecore of ferromagnetic material. This arc section 7 normally displays thesame width (y) as the shanks 5 a, 5 b.

[0020] The shanks 5 a, 5 b further display a tapering cross section,seen in a direction from their respective second ends towards theirrespective first ends, a thickness a of said first end of a shank beingin relation to a thickness b of said second end of this shank in such amanner that b/10<a<b/2, preferably b/5<a<b/3. Thanks to the taperingcross section towards the air gasp 6, there will be obtained aconcentration of the magnetic flow 8 in the air gap 6, as indicated inFIG. 2.

[0021] In order that the apparatus may be placed closely adjacent,abutting against, or urging against a planar packaging material 9 whichincludes a metal layer and a polymer layer, said shanks 5 a, 5 b areprovided with planar outer defining surfaces which are disposed in oneand the same plane with each other, or arched (convex or concave) outerdefining surfaces which are disposed to follow one and the sameimaginary arc of a circle (e.g. a drum or roller). The normal placing ofthe apparatus in relation to the packaging laminate 9 is apparent fromFIG. 2. At the air gap 6, a current is induced in the metal layer of thepackaging laminate in the manner which is apparent from FIG. 3, whichthus shows induced current circles 10 in the metal layer of a packaginglaminate 9 with an inductor according to the present invention disposedthereunder, seen from above. At a position corresponding to the air gap6, these current circles are concentrated, heat being generated in themetal layer of the packaging laminate 9. From the point of view ofinduction, it is of less or no consequence in which direction thepackaging material 9 is turned, i.e. whether its metal layer (aluminiumfoil) is turned to face the induction apparatus, or whether it is turnedto face away from it, with, for example, a core layer of paper orpaperboard between the metal layer and the induction apparatus. On spotheating, a stay time of 30-500 milliseconds is normally required,preferably 40-300 milliseconds.

[0022]FIG. 4 shows how the apparatus may be built up with a core 1 whichis formed as a toroid, i.e. with an arc section 7 which follows an arcof a circle, with an upper region bevelled to a planar outer definingsurface of two shanks 5 a, 5 b and with an air gap 6 therebetween. Anouter, maximum dimension of the core 1, corresponding to an outerdiameter in FIG. 4, is suitably 60-150 mm, preferably 80-120 mm, whilean inner dimension of the core 1, corresponding to an inner diameter inFIG. 4, is 20-40 mm less than the outer dimension.

[0023] In the apparatus according to the present invention, the coil 2is advantageously wound around the arc section 7 of the core 1, whichimplies that it need not be disposed for abutment against the packagingmaterial or even close to it. The coil 2 may be disposed in a pluralityof different ways, it however preferably displaying 1-10 turns,preferably 2-8 turns and even more preferably 2-6 turns around the arcsection 7 of the core 1. FIG. 1 shows how the coil 2 is formed from asingle turn of a metal strip of e.g. copper or silver, while FIG. 2shows how the coil 2 is formed from four turns of copper or silver wireor so-called Litz-wire. FIG. 4 shows how the coil may be formed from,e.g. four separate metal strips which are each wound one turn around thearc section 7 of the core and interconnected in connection points 11 a,11 b, 11 c into a whole coil with, in the illustrated case, four turns.Typically, the metal strips are roughly 20 mm wide and display athickness of about 0.5 mm. The free, outer ends of the outermost metalstrip display connection points/connections 3 a, 3 b for a capacitor. Anexternal, high frequency current source (shown in FIG. 2) may beconnected between two of the connection points 3 a, 3 b, 11 a, 11 b, 11c, depending upon impedance.

[0024]FIGS. 5 and 6 show yet a further method of realising a coil 2 withseveral turns. Here, a metal strip which corresponds to the total widthof the coil has been wound in mutually superjacent turns, withinsulation 12 between them. From an inner end of the metal strip, anarrow strand has been drawn out through a small hole in the superjacentlayers of metal strip, so that two connection points 3 a, 3 b for thecoil 2 have been realised.

[0025] In FIG. 2, but valid for all embodiments, it is shown how theconnection points 3 a, 3 b of the coil 2 are coupled to a capacitor 13and how two of the connection points 3 a, 3 b, 11 a, 11 b, 11 c of thecoil 2 are connected to a high frequency generator 4. The frequencyutilised is typically 100-1,000 kHz, preferably 200-600 kHz.

[0026] The present invention is not restricted to the illustratedembodiments, but may be modified without departing from the scope of theappended claims.

What is claimed is:
 1. An apparatus in the production of a package or apackaging material comprising at least one metal layer and one polymerlayer, the apparatus including an inductor connectable to a highfrequency current source, characterised in that said inductor includes acore (1) of a ferromagnetically conductive material, the core displayingtwo shanks (5 a, 5 b) with an air gap (6) between a first respective endof these shanks (5 a, 5 b) and an arc section (7) which interconnects asecond respective end of the two shanks (5 a, 5 b) to each other forconducting a magnetic flow (8) between the shanks, said arc section (7)displaying an electrically conductive coil (2) wound around same, thecoil displaying connection points (3 a, 3 b, 11 a, 11 b, 11 c) for saidhigh frequency current source (4).
 2. The apparatus as claimed in claim1, characterised in that said shanks (5 a, 5 b) display a width (y) ofat least 10 mm, but less than 50 mm, preferably less than 40 mm and evenmore preferably less than 30 mm, seen in a direction of extent at rightangles to a direction of extent of said air gap (6) between the firstrespective ends of said shanks (5 a, 5 b).
 3. The apparatus as claimedin claim 1, characterised in that said shanks (5 a, 5 b) display a width(y) of least 10 mm, but at most 200 mm, preferably at most 150 mm, seenin a direction of extent at right angles to a direction of extent ofsaid air gap (6) between the first respective ends of said shanks (5 a,5 b).
 4. The apparatus as claimed in claim 1, characterised in that saidair gap (6) displays a length (x) of at least 5 mm, preferably at least10 mm, but less than 50 mm, preferably less than 40 mm and even morepreferably less than 30 mm, seen in a direction of extent of said airgap between the first respective ends of said shanks (5 a, 5 b).
 5. Theapparatus as claimed in any of the preceding claims, characterised inthat said shanks (5 a, 5 b) are provided with planar outer definingsurfaces which are disposed in one and the same plane or with archedouter defining surfaces which are disposed to follow one and the sameimaginary arc of a circle.
 6. The apparatus as claimed in any of thepreceding claims, characterised in that said shanks (5 a, 5 b) display atapering cross section, seen in a direction from their respective secondends towards their respective first ends, a thickness (a) of said firstend of a shank being in relation to a thickness (b) of said second endof this shank such that b/10<a<b/2, preferably b/5<a<b/3, forconcentrating the magnetic flow (8) in the air gap (6).
 7. The apparatusas claimed in any of the preceding claims, characterised in that saidcore (1) is designed so that the arc section (7) follows an arc of acircle.
 8. The apparatus as claimed in any of the preceding claims,characterised in that said ferromagnetically conductive material in thecore (1) displays a permeability of μr 500-8,000, even more preferablyμr 2,000-8,000.
 9. The apparatus as claimed in any of the precedingclaims, characterised in that said coil (2) is wound 1-10 turns,preferably 2-8 turns and even more preferably 2-6 turns around the arcsection (7) of the core (1).
 10. The apparatus as claimed in any of thepreceding claims, characterised in that said coil (2) consists of ametal strip or a wire, preferably of copper or silver, which is formedinto a coil around the arc section (7) of the core (1).
 11. Theapparatus as claimed in any of the preceding claims, characterised inthat it also includes means for removing a confetti from the package orthe packaging laminate in said air gap.